Effects of lentivirus-delivered short hairpin RNA targeting human papillomavirus 16 E7 gene on the expression of DNA methyltransferases in SiHa cells / 中华皮肤科杂志

ABSTRACT

Objective To evaluate the effects of lentivirus-delivered short hairpin RNA (shRNA) targeting human papillomavirus 16 (HPV16) E7 gene on the expression of 4 kinds of DNA methyltransferases (DNMTs),including DNMT1,DNMT3A,DNMT3B and DNMT3L,in HPV16-positive cervical cancer cell line SiHa.Methods The recombinant plasmid containing HPV16 E7 gene-targeting shRNA was constructed firstly.Then,the BLOCK-iTTM lentiviral RNAi expression system kit was used to package the lentiviral vector,which was transfected into 293T cells.The lentivirus-containing supernatants were collected at 48 and 72 hours after transfection.The SiHa cells were divided into 3 groups to be cultured with lentiviral supernatant containing HPV16 E7 gene-targeting shRNA recombinant plasmids mixed with complete medium at a ratio of 1:1 (shRNA group),lentiviral supernatant containing empty plasmids mixed with complete medium at a ratio of 1:1 (negative control group),and complete medium alone (blank control group),respectively.Real-time fluorescence-based quantitative PCR (qRT-PCR) was performed to measure mRNA expression of HPV16 E7 and 4 kinds of DNMTs in the above 3 groups at 0,48,96 hours after infection,and Western blot analysis to determine protein expression of the 4 DNMTs at 48,96 hours after infection.Results There were no significant differences in the mRNA expression of HPV16 E7 and the 4 DNMTs among the shRNA group,negative control group and blank control group at 0 hour after infection (all P ＞ 0.05).At 48,96 hours after infection,the mRNA expression of HPV16 E7 and the 4 DNMTs decreased significantly in the shRNA group compared with the negative control group and blank control group (all P ＜ 0.05),but did not differ between the negative control group and blank control group (all P ＞ 0.05).Additionally,E7,DNMT1,DNMT3A,DNMT3B and DNMT3L gene-silencing efficiencies in the shRNA group were 71.13％,50.53％,13.72％,46.27％ and 17.92％ at 48 hours,and 83.50％,74.2％,47.8％,64.7％ and 48.9％ at 96 hours after infection,respectively.Western blot analysis showed that the protein expression of the 4 DNMTs significantly decreased in the shRNA group compared with the negative control group and blank control group at 48,96 hours after infection (all P ＜ 0.01).Moreover,the protein expression of DNMT1,DNMT3A,DNMT3B and DNMT3L in the shRNA group gradually decreased over time,and was inhibited by 84％,37.2％,59.8％ and 49.3％ at 48 hours respectively,and by 73.1％,68.7％,55.5％ and 65.5％ at 96 hours after infection respectively.Conclusion Targeted silencing of E7 gene in HPV16-positive SiHa cells can interfere with the mRNA and protein expression of DNMT1,DNMT3A,DNMT3B and DNMT3L.